The present invention relates generally to synthetic wood composite materials. More particularly, the present invention is directed to a cellulose/polyolefin composite pellet and related manufacturing methods. The pellet may be used to manufacture a wide variety of components.
The supply of natural woods for construction and other purposes is dwindling. As a result, many are concerned about conserving the world""s forests, as the cost of natural woods has risen. Because of the extensive time needed to replenish forests, a tremendous demand has developed in recent years for alternative composites that look and feel like natural woods.
In response, many composites, such as cellulosic/polymer composites, are used as replacements for all-natural wood, particleboard, wafer board, and other similar material. For example, U.S. Pat. Nos. 3,908,902, 4,091,153, 4,686,251, 4,708,623, 5,002,713, 5,005,247, 5,087,400, and 5,151,238 relate to processes for making wood replacement products. As compared to natural woods, cellulosic/polymer composites offer superior resistance to wear and tear. In particular, cellulosic/polymer composites have enhanced resistance to moisture. In fact, it is well known that the retention of moisture is a primary cause of the warping, splintering, and discoloration of natural woods. Moreover, cellulosic/polymer composites have the appearance of natural wood, and they may be sawed, sanded, shaped, turned, fastened, and finished in the same manner as natural woods. Consequently, cellulosic/polymer composites are commonly used for applications such as interior and exterior decorative house moldings, picture frames, furniture, porch decks, deck railings, window moldings, window components, door components, roofing structures, building siding, and other suitable indoor and outdoor components.
Nevertheless, those skilled in the art have recognized that excessive moisture content in a synthetic wood composition may result in a poor quality end product. In particular, excessive moisture content in a synthetic wood composition may result in an end component that is susceptible to cracking, blistering, and deteriorating appearance. Consequently, it may be necessary to dry any cellulosic material to a predetermined level prior to introducing it into the synthetic wood composition. Even after the cellulosic material is dried, it has a natural tendency to reabsorb moisture from the environment. As a result, it may also be necessary to store the dried cellulosic material in a moisture controlled environment in order to prevent the cellulosic material from reabsorbing additional moisture before being added to the synthetic wood composition. In light of these considerations, it may be difficult and costly to maintain sufficiently dry cellulosic material while shipping it between different locations.
The present invention relates generally to composite materials. The present invention includes several different formulations and material composites including, but not limited to, formulations that include cellulosic material and/or inorganic material. The filler material may be mixed with a polyolefin material to make a variety of components. In addition, the composition of the present invention may be used as an alternative to natural wood, other synthetic wood compositions, plastics, metals, and other conventional materials for making various types of components.
The present invention provides various compositions wherein some or all of the ingredients may be combined to form pellets. The pellets may be shipped to various manufacturing locations substantially without reabsorbing a detrimental amount of moisture content. An exemplary embodiment of the composite pellet may comprise at least one polyolefin material and at least one cellulosic material. The pellet may also include some or all of any other desired ingredients of the composition including, but not limited to, stabilizers, lubricants, process aids, inorganic fillers, accelerators, inhibitors, enhancers, compatibilizers, blowing agents, foaming agents, thermosetting materials, colorants, and other similar, suitable, or conventional additives. If the pellet does not include all of the ingredients of the composition, the remaining ingredients may be combined with the pellets prior to forming the end product. For example, additional polyolefin material may be mixed with the pellets in a dry mixing device and/or in a blending device, e.g., an extruder, if the pellets do not include the entire amount of the polyolefin material. For another example, some or the entire amount of the other additives may be mixed with the pellets in a dry mixing device and/or in a blending device, e.g., an extruder, if not included in the pellets at all or in their entirety.
In addition to the novel features and advantages mentioned above, other objects and advantages of the present invention will be readily apparent from the following descriptions of the drawings and exemplary embodiments.